Rigidity-adjustable robot joint based on series elastic drivers

Abstract

The invention relates to the technical field of robot motion, in particular to a rigidity-adjustable robot joint based on a series elastic driver, which comprises a motor with an encoder, a harmonic reducer, a flange plate, a first connecting plate, a second connecting plate, a bearing, a series elastic body, an end cover and a magnetic encoder, and the harmonic reducer comprises a wave generator, a flexible gear and a rigid gear; the output end of the motor with the encoder is connected with the wave generator, the first connecting plate is fixedly connected with the flexible gear, the flange plate and the second connecting plate are arranged on the rigid gear in a sleeving mode, and the second connecting plate covers the end face of the flange plate. One side of the series elastomer is connected with the second connecting plate, and the other side is fixedly connected with the end cover. The joint solves the problems that an existing robot joint is not compact in structure, difficult to output precise torque and low in transmission precision, and is used for robots.

Description

Technical Field

[0001] The invention relates to the technical field of robot motion, in particular to an adjustable stiffness robot joint based on a series elastic driver. Background Art

[0002] Robot joints are one of the key components of robots, responsible for transmitting power and achieving movement. With the rapid development of robotics technology, especially in the fields of service robots, exoskeleton robots, industrial robots, etc., the design and performance of robot joints have a direct impact on the robot's movement ability and flexibility.

[0003] The traditional driver used in robot joints is a rigid driver, but rigid drive joints may cause a series of safety issues due to insufficient flexibility and difficulty in current control in torque control. For example, when facing excessive impact, the lack of buffering may lead to damage to their own structure and function. Flexible joints are flexible due to the design of elastic elements, which can resist impact and sense force, but they have problems such as lack of reliability, narrow bandwidth, slow response and lack of precision. Summary of the invention

[0004] The present invention provides an adjustable stiffness robot joint based on a series elastic drive. The joint achieves adjustable stiffness by introducing a specially made series elastic body, avoids the basic performance limitations of conventional series elastic bodies, and solves the problems of existing robot joints having a non-compact structure, difficulty in outputting precise torque, and low transmission accuracy.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A robot joint with adjustable stiffness based on a series elastic drive comprises a motor with an encoder, a harmonic reducer, a flange, a first connecting plate, a second connecting plate, a bearing, a series elastic body, an end cover, a magnetic encoder, a joint fixed end and a joint motion end; the harmonic reducer comprises a wave generator, a flexible wheel and a rigid wheel, the waveform generator is assembled in the inner circle of the flexible wheel, the rigid wheel meshes with the flexible wheel, and the harmonic reducer is used in a connection mode in which the flexible wheel end is fixed and the rigid wheel end is output; the output end of the motor with the encoder is connected to the wave generator, and the first connecting plate is fixedly connected to the flexible wheel; the flange and the second connecting plate are sleeved on the rigid wheel and fixedly connected to the rigid wheel, and the second connecting plate is covered on the end surface of the flange; one side of the series elastic body is connected to the second connecting plate, and the other side is fixedly connected to the end cover, and a magnetic encoder is installed at one end of the end cover; the lower part of the joint fixed end is fixedly connected to the first connecting plate, and the joint motion end is fixedly connected to the lower end of the end cover.

[0006] Furthermore, the series elastomer includes an outer ring output structure, an inner ring rotating structure and an elastic element, the inner ring rotating structure is connected to the inner ring of the bearing, the inner side of the outer ring output structure is connected to the outer ring of the bearing, and the right end of the outer ring output structure is fixedly connected to the end cover.

[0007] Furthermore, the outer ring output structure includes an output housing, four spring fixing blocks and screws, the spring fixing blocks are fixedly connected to the corners of the output housing by screws, and the output housing is connected to the outer ring of the bearing.

[0008] Furthermore, the elastic element of the series elastic body includes four groups of springs and four groups of spring pins, one end of the spring pin is connected to the inner ring rotating structure, and the other end is connected to the spring fixing block, and the spring is sleeved on the spring pin.

[0009] Furthermore, the inner ring rotating structure includes an internal rotating shaft and four electromagnetic assemblies. The outer side of the internal rotating shaft is connected to the inner ring of the bearing, one end of the internal rotating shaft is connected to the second connecting plate, and the internal rotating shaft rotates synchronously with the rigid wheel and the second connecting plate; the electromagnetic assembly includes an electromagnetic rod and an electromagnetic rod sleeve, the electromagnetic rod is arranged circumferentially along the internal rotating shaft, the electromagnetic rod sleeve is in contact with the spring, and the electromagnetic rod sleeve slides on the spring pin; the power supply of each electromagnetic rod is independently controlled by the control end, and when power is supplied, the electromagnetic rod pops out into the electromagnetic rod sleeve.

[0010] Furthermore, each group of springs includes two springs, denoted as a first spring and a second spring, the electromagnetic rod sleeve is located between the first spring and the second spring, and the first spring and the second spring are both abutted between the corresponding spring fixing block and the electromagnetic rod sleeve; each group of spring pins also includes two spring pins, denoted as a first spring pin and a second spring pin, and the first spring pin and the second spring pin correspond to the first spring and the second spring respectively.

[0011] Furthermore, the electromagnetic rod and the electromagnetic rod sleeve of the series elastic body are plugged in a triangular structure, and the electromagnetic rod can be adaptively ejected into the electromagnetic rod sleeve.

[0012] Furthermore, when one group of electromagnetic rods is energized and bounces into the electromagnetic rod sleeve and extends to the middle of the spring, only one group of springs participates in the movement, and the series elastomer is in a low stiffness mode; when two groups of electromagnetic rods are energized and extended to the middle of the spring, the two groups of springs work in series, and the series elastomer is in a medium-low stiffness mode; when three groups of electromagnetic rods are energized and extended to the middle of the spring, the three groups of springs work in series, and the series elastomer is in a medium stiffness mode; when four groups of electromagnetic rods are energized and extended to the middle of the spring, the four groups of springs work in series, and the series elastomer is in a high stiffness mode, the electromagnetic rods will bounce back at the moment of power failure, and the four groups of electromagnetic rods will be disconnected from the electromagnetic rod sleeve, so that the internal rotating shaft of the series elastomer is separated from the outer ring output housing.

[0013] Furthermore, the motor with encoder is a hollow frameless torque motor, the harmonic reducer is a hollow harmonic reducer, and the magnetic encoder adopts a hollow encoder.

[0014] Furthermore, an inertial measurement unit is installed on the joint motion end.

[0015] Furthermore, the joint motion end is a telescopic structure. Furthermore, the electromagnetic rod will rebound at the moment of power failure, the four sets of electromagnetic rods are disconnected from the electromagnetic rod sleeves, and the internal rotating shaft of the series elastic body is separated from the outer ring output housing.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention is suitable for flexible joints used in the field of robots. The power of the frameless torque motor is decelerated by a harmonic accelerator and converted into the rotational power output of the joint. The application of the frameless torque motor and the harmonic reducer makes the joint structure compact and the movement accuracy high.

[0017] Second, the present invention adopts a self-designed series elastic body, which adopts a split structure, is easy to assemble, and makes the joint have good impact resistance; the elastic body has four groups of symmetrically distributed compression springs, which are extended to the middle of the spring by different numbers of electromagnetic rods. The elastic body can obtain four stiffnesses in total to meet the stiffness requirements of robot joints in different working conditions. The electromagnetic rod can rebound at the moment of power failure, so that the elastic body rotating shaft is separated from the outer ring output housing, that is, the drive device is separated from the execution end, so that the joint can effectively prevent accidental injuries caused by instantaneous large impacts during movement.

[0018] 3. The joint has two encoders, one is the motor's built-in encoder, which is used to measure the rotation angle of the motor output end, and the other is a magnetic encoder placed on the end cover, which is used to measure the movement angle of the actuator. The flexible deformation is characterized by the angle difference between the two encoders. The product of the angle difference and the stiffness value of the elastomer can obtain the precise output torque of the joint, which can ensure good motion control characteristics of the joint.

[0019] 4. The frameless motor, harmonic reducer, and magnetic encoder are all hollow in design, and the cables can be routed through the center of the joint, which protects the cables without affecting the rotation of the joint.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention is suitable for flexible joints used in the field of robots. The power of the frameless torque motor is decelerated by a harmonic accelerator and converted into the rotational power output of the joint. The application of the frameless torque motor and the harmonic reducer makes the joint structure compact and the movement accuracy high.

[0021] Second, the present invention adopts a self-designed series elastic body, which adopts a split structure, is easy to assemble, and makes the joint have good impact resistance; the elastic body has four groups of symmetrically distributed compression springs, which are extended to the middle of the spring by different numbers of electromagnetic rods. The elastic body can obtain four stiffnesses in total to meet the stiffness requirements of robot joints in different working conditions. The electromagnetic rod can rebound at the moment of power failure, so that the elastic body rotating shaft is separated from the outer ring output housing, that is, the drive device is separated from the execution end, so that the joint can effectively prevent accidental injuries caused by instantaneous large impacts during movement.

[0022] 3. The joint has two encoders, one is the motor's built-in encoder, which is used to measure the rotation angle of the motor output end, and the other is a magnetic encoder placed on the end cover, which is used to measure the movement angle of the actuator. The flexible deformation is characterized by the angle difference between the two encoders. The product of the angle difference and the stiffness value of the elastomer can obtain the precise output torque of the joint, which can ensure good motion control characteristics of the joint.

[0023] 4. The frameless motor, harmonic reducer, and magnetic encoder are all hollow in design, and the cables can be routed through the center of the joint, which protects the cables without affecting the rotation of the joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A three-dimensional diagram of the overall structure of an adjustable stiffness robot joint based on a series elastic driver according to the present invention; Figure 2 It is a three-dimensional diagram of the overall structure of an adjustable stiffness robot joint based on a series elastic drive according to the present invention from another angle; Figure 3 It is a main cross-sectional view of the overall structure of the present invention; Figure 4 A three-dimensional diagram of a series elastic body of the present invention; Figure 5 It is a front view of the series elastic body of the present invention; Figure 6 An exploded view of the present invention; Figure 7 It is a schematic diagram of multi-stiffness of the series elastic body of the present invention; Figure 8 It is the spring adaptive flow chart of the present invention.

[0025] In the figure, 1. motor with encoder; 2. harmonic reducer; 2-1. waveform generator; 2-2. flexible wheel; 2-3. rigid wheel; 3. flange; 4. first connecting plate; 5. second connecting plate; 6. bearing; 7. series elastic body; 7-1. outer ring output structure; 7-2. inner ring rotating structure; 7-3. elastic element; 8. end cover; 9. magnetic encoder; 10. joint fixed end; 11. joint moving end; 12. inertial measurement unit; 13. adjusting bolt; 14. adjusting nut; 15. output housing; 16. spring fixing block; 17. screw; 18. spring; 18-1. first spring; 18-2. second spring; 19. spring pin; 20. internal rotating shaft; 21. electromagnetic assembly; 21-1. electromagnetic rod; 21-2. electromagnetic rod sleeve. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0027] Combination Figure 1-Figure 6 The present embodiment is described. The present invention is an adjustable stiffness robot joint based on a series elastic drive, comprising a motor 1 with an encoder, a harmonic reducer 2, a flange 3, a first connecting plate 4, a second connecting plate 5, a bearing 6, a series elastic body 7, an end cover 8, a magnetic encoder 9, a joint fixed end 10 and a joint motion end 11; the harmonic reducer 2 comprises a wave generator 2-1, a flexible wheel 2-2 and a rigid wheel 2-3, the wave generator 2-1 is assembled in the inner circle of the flexible wheel 2-2, and the rigid wheel 2-3 and the flexible wheel 2- 2 meshing, the harmonic reducer is used in a connection mode in which the flexible wheel end is fixed and the rigid wheel end is output; the output end of the motor 1 with an encoder is connected to the wave generator 2-1, and the first connecting plate 4 is fixedly connected to the flexible wheel 2-2; the flange 3 and the second connecting plate 5 are sleeved on the rigid wheel 2-3 and fixedly connected to the rigid wheel 2-3, and the second connecting plate 5 covers the end surface of the flange 3; one side of the series elastic body 7 is connected to the second connecting plate 5, and the other side is fixedly connected to the end cover 8, and a magnetic encoder 12 is installed at one end of the end cover 8.

[0028] See also Figure 4 and Figure 6 As shown, the series elastic body 7 includes an outer ring output structure 7-1, an inner ring rotating structure 7-2 and an elastic element 7-3, the inner ring rotating structure 7-2 is connected to the inner ring of the bearing 6, the inner side of the outer ring output structure 7-1 is connected to the outer ring of the bearing 6, and the right end of the outer ring output structure 7-1 is fixedly connected to the end cover 8. In this embodiment, the bearing 6 adopts a deep groove ball bearing 6.

[0029] See also Figure 5As shown, the outer ring output structure 7 - 1 includes an output housing 15 , four spring fixing blocks 16 and screws 17 . The spring fixing blocks 16 are fixedly connected to the corners of the output housing 15 by screws 17 , and the output housing 15 is connected to the outer ring of the bearing 6 .

[0030] See also Figure 5 As shown, the elastic element 7 - 3 of the series elastomer 7 includes four groups of springs 18 and four groups of spring pins 19 , one end of the spring pin 19 is connected to the inner ring rotating structure 7 - 2 , and the other end is connected to the spring fixing block 16 , and the spring 18 is sleeved on the spring pin 19 .

[0031] See also Figure 4 , 5 As shown in Figure 6, the inner ring rotating structure 7-1 includes an internal rotating shaft 20 and four electromagnetic assemblies 21. The outer side of the internal rotating shaft 20 is connected to the inner ring of the bearing 6, and one end of the internal rotating shaft 20 is connected to the second connecting plate 5. The internal rotating shaft 20 rotates synchronously with the rigid wheel 2-2 and the second connecting plate 5; the electromagnetic assembly 21 includes an electromagnetic rod 21-1 and an electromagnetic rod sleeve 21-2. The electromagnetic rod 21-1 is arranged along the circumference of the internal rotating shaft 20, the electromagnetic rod sleeve 21-2 is connected to the spring 18, and the electromagnetic rod 21-1 slides on the spring pin 19; the power supply of each electromagnetic rod is independently controlled by the control end, and the electromagnetic rod 21 will pop out into the electromagnetic rod sleeve 21-2 when it is energized. When working, the assembly pushes the spring to move.

[0032] See also Figure 5 As shown, each group of springs 18 includes two springs, which are denoted as the first spring 18-1 and the second spring 18-1, and the electromagnetic rod sleeve 21-2 is located between the first spring 18-1 and the second spring 18-2, and the first spring 18-1 and the second spring 18-2 are both in contact with the corresponding spring fixing block 16 and the electromagnetic rod sleeve 21-2. Each group of spring pins 19 also includes two spring pins, which are denoted as the first spring pin and the second spring pin, and the first spring pin and the second spring pin correspond to the first spring 18-1 and the second spring 18-2 respectively.

[0033] Combination Figure 8 It is noted that in this embodiment, the electromagnetic rod 21 - 1 and the electromagnetic rod sleeve 21 - 2 of the series elastic body 7 are plugged in a triangular structure, so that the electromagnetic rod sleeve 21 - 2 can adaptively snap into the electromagnetic rod 21 - 1 .

[0034] Combination Figure 7 , 8It is explained that in this embodiment, when a group of electromagnetic rods 21-1 of the series elastic body 7 is energized and bounces into the electromagnetic rod sleeve 21-2, and when it stretches to the middle of the spring 18, only one group of springs 18 participates in the movement, and the series elastic body 7 is in the low stiffness mode; when two groups of electromagnetic rods 21-1 are stretched to the middle of the spring 18, the two groups of springs 18 work in series, and the series elastic body 7 is in the medium-low stiffness mode; when three groups of electromagnetic rods 21-1 are stretched to the middle of the spring 18, the three groups of springs 18 work in series, and the series elastic body 7 is in the medium stiffness mode; when four groups of electromagnetic rods 21-1 are all stretched to the middle of the spring 18, the four groups of springs 18 work in series, and the series elastic body 7 is in the high stiffness mode; the electromagnetic rods 21-1 will bounce back at the moment of power failure, and the four groups of electromagnetic rods 21-1 are all disconnected from the spring 18, and the internal rotating shaft 20 of the series elastic body 7 is separated from the outer ring output housing 15.

[0035] Combination Figure 3 It is explained that the harmonic reducer 2 in this embodiment has the advantages of high precision, large transmission ratio, compact structure, etc. The motor 1 with encoder is a hollow frameless torque motor, the harmonic reducer 2 is a hollow harmonic reducer, and the magnetic encoder 12 adopts a hollow encoder. With such a configuration, the joint routing is stable, the cables are protected, and the joint is safe and reliable.

[0036] Combination Figure 1 , 3 It is noted that in this embodiment, the lower portion of the joint fixed end 10 is fixedly connected to the first connecting plate 4 , and the joint motion end 11 is fixedly connected to the lower end of the end cover 8 ; an inertial measurement unit 12 is mounted on the joint motion end 11 .

[0037] Combination Figure 6 It is explained that the joint motion end 11 is a telescopic structure. In this embodiment, the joint motion end 11 has a slide groove and three bolt holes. By installing the adjusting bolt 13 and the adjusting nut 14 in different holes, the length of the joint motion end 11 can be extended or retracted.

[0038] The working principle of the adjustable stiffness robot joint based on the series elastic drive of the present invention is: The motor 1 with encoder transmits the torque to the harmonic reducer 2, and the torque is transmitted to the second connecting plate 5 through the amplification effect of the harmonic reducer 2; the second connecting plate 5 rotates synchronously with the internal rotating shaft 20 of the series elastic body 7, and the output housing 15 of the series elastic body 7 is connected to the internal rotating shaft 20 through the inner and outer rings of the bearing 6, and the spring 18 is installed on the output housing 15. The internal rotating shaft 20 and the output housing 15 generate relative displacement to compress the spring 18, and the spring 18 drives the output housing 15 to move.

[0039] Assumptions n A group of springs 18 participates in the movement, and the stiffness of a group of springs 18 is kWhen one set of electromagnetic rods 21 is powered on and bounces into the electromagnetic rod sleeve 22 and stretches to the middle of the spring 18, only one set of springs 18 participates in the movement, and the elastic body is in a low stiffness mode with a stiffness of k; when two sets of electromagnetic rods 21 stretch to the middle of the spring 18, the two sets of springs 18 work in series, and the elastic body is in a medium-low stiffness mode with a stiffness of 2× k When the three sets of electromagnetic rods 21 are extended to the middle of the spring 18, the elastic body is in the medium stiffness mode, with a stiffness of 3× k When the four sets of electromagnetic rods 21 are all extended to the middle of the spring 18, the elastic body is in a high stiffness mode with a stiffness of 4× k .

[0040] The rotation angle difference between the inner and outer rings of the series elastic body 7 can be measured by using the encoder provided by the motor 1 and the magnetic encoder 9 installed on the side of the end cover 8. θ , the joint output torque can be accurately measured M : M = n × k × θ , to perform position control or speed control of the joint.

[0041] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "back", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0042] In addition, unless otherwise clearly specified and limited, the terms, "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. The specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. An adjustable stiffness robot joint based on a series elastic actuator, characterized in that: The invention comprises a motor (1) with an encoder, a harmonic reducer (2), a flange (3), a first connecting plate (4), a second connecting plate (5), a bearing (6), a series elastic body (7), an end cover (8), a magnetic encoder (9), a joint fixing end (10) and a joint motion end (11); the harmonic reducer comprises a wave generator (2-1), a flexible wheel (2-2) and a rigid wheel (2-3); the wave generator (2-1) is assembled in the inner circle of the flexible wheel (2-2), and the rigid wheel (2-3) is meshed with the flexible wheel (2-2); the output end of the motor (1) with an encoder is connected to the flexible wheel (2-2); The invention relates to a wave generator (2-1), a first connecting plate (4) and a flexible wheel (2-2) being fixedly connected; a flange (3) and a second connecting plate (5) are sleeved on the rigid wheel (2-3) and fixedly connected to the rigid wheel (2-3), and the second connecting plate (5) covers the end surface of the flange (3); one side of the series elastic body is connected to the second connecting plate, and the other side is fixedly connected to the end cover, and a magnetic encoder (9) is installed at one end of the end cover (8); the lower part of the joint fixed end (10) is fixedly connected to the first connecting plate (4), and the joint motion end (11) is fixedly connected to the lower end of the end cover (8).

2. The adjustable stiffness robot joint based on the series elastic actuator according to claim 1, characterized in that: The series elastic body (7) includes an outer ring output structure (7-1), an inner ring rotating structure (7-2) and an elastic element (7-3), the inner ring rotating structure (7-2) is connected to the inner ring of the bearing (6), the inner side of the outer ring output structure (7-1) is connected to the outer ring of the bearing (6), and the right end of the outer ring output structure (7-1) is fixedly connected to the end cover (8).

3. The adjustable stiffness robot joint based on the series elastic actuator according to claim 2, characterized in that: The outer ring output structure (7-1) of the series elastic body (7) comprises an output housing (15), four spring fixing blocks (16) and screws (17); the spring fixing blocks (16) are fixedly connected to the corners of the output housing (15) by means of screws (17); and the output housing (15) is connected to the outer ring of the bearing (6).

4. The adjustable stiffness robot joint based on the series elastic actuator according to claim 2, characterized in that: The elastic element (7-3) of the series elastic body (7) includes four groups of springs (18) and four groups of spring pins (19), one end of the spring pin (19) is connected to the inner ring rotating structure (7-2), and the other end is connected to the spring fixing block (16), and the spring (18) is sleeved on the spring pin (19).

5. The adjustable stiffness robot joint based on the series elastic actuator according to claim 4, characterized in that: The inner ring rotating structure (7-2) of the series elastic body (7) comprises an internal rotating shaft (20) and four electromagnetic assemblies (21); the outer side of the internal rotating shaft (20) is connected to the inner ring of the bearing (6); one end of the internal rotating shaft (20) is fixedly connected to the second connecting plate (5); the internal rotating shaft (20) rotates synchronously with the rigid wheel (2-3) and the second connecting plate (5); the electromagnetic assembly comprises an electromagnetic rod (21-1) and an electromagnetic rod sleeve (21-2); the electromagnetic rod (21-1) is arranged along the circumference of the internal rotating shaft (20); the electromagnetic rod sleeve (21-2) is in contact with the spring (18); the electromagnetic rod (21-1) sleeve slides on the spring pin (19); the power supply of each electromagnetic rod is independently controlled by the control end; when the power is supplied, the electromagnetic rod (21-1) pops out into the electromagnetic rod sleeve (21-2).

6. The adjustable stiffness robot joint based on the series elastic actuator according to claim 5, characterized in that: Each group of springs (18) includes two springs, which are denoted as a first spring (18-1) and a second spring (18-1). The electromagnetic rod sleeve (21-2) is located between the first spring (18-1) and the second spring (18-2). The first spring (18-1) and the second spring (18-2) are both in contact with the corresponding spring fixing block (16) and the electromagnetic rod sleeve (21-2). Each group of spring pins (19) also includes two spring pins, which are denoted as a first spring pin and a second spring pin. The first spring pin and the second spring pin correspond to the first spring (18-1) and the second spring (18-2) respectively.

7. The adjustable stiffness robot joint based on serial elastic actuator according to claim 5, characterized in that: The electromagnetic rod (21-1) and the electromagnetic rod sleeve (21-2) of the series elastic body (7) are plugged in a triangular structure, and the electromagnetic rod (21-1) can adaptively spring into the electromagnetic rod sleeve (21-2).

8. The adjustable stiffness robot joint based on a series elastic actuator according to claim 1, characterized in that: The motor (1) with encoder is a hollow frameless torque motor, the harmonic reducer (2) is a hollow harmonic reducer, and the magnetic encoder (9) is a hollow encoder.

9. The adjustable stiffness robot joint based on a series elastic actuator according to claim 1, characterized in that: An inertial measurement unit (12) is installed on the joint motion end (11).

10. The adjustable stiffness robot joint based on a series elastic actuator according to claim 1, characterized in that: The joint motion end (11) is a telescopic structure.

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